This invention relates to parachutes and more particularly to a canopy opening assist and control arrangement for limiting the opening shock when a parachute is opened rapidly.
The concept of using some technique to assist in the initial opening of the mouth of a parachute is known. What is used is a small auxiliary parachute shaped canopy that has a series of lines which are connected to the confluence point of the load lines of the main canopy. This auxiliary parachute is positioned, when the parachutes are folded or squidded, near the mouth of the main parachute. In the initial stages of opening, the auxiliary parachute opens immediately thereby making sure that the mouth of the main parachute opens immediately. The faster opening attained by this technique generally results in an opening shock increase of approximately 10% when the parachute opens at air speeds of 120 to 130 knots. This increase in opening shock limits the benefits of this type of auxiliary canopy to applications where the air speed on opening is no greater than approximately 130 knots.
Accordingly, one of the major purposes of this invention is to provide a means to assist in the opening of the mouth of the parachute which avoids increasing the opening shock particularly at high air speeds, meaning speeds above 130 knots.
One of the conditions under which high air speed opening occurs is after a pilot is ejected from an airplane. Under such conditions, the air speed at the time of parachute deployment is frequently 300 knots or more. Yet a pilot sometimes has to be ejected from an airplane when the airplane is flying at a relatively slow speed and at a low altitude. Thus it is important that the parachute open as soon as possible and an opening assist mechanism is of considerable importance. The prior art opening assist mechanisms tend to cause the opening to proceed at a rate which creates a substantial increase in opening shock. This increased opening shock is highly dangerous for the individual at the higher ejection speeds.
Accordingly, it is a related purpose of this invention to provide a parachute opening assist mechanism which can safely be used with a pilot ejector mechanism at various combinations of ejection speeds and altitudes, including relatively low speed at low altitude and relatively high speed at any altitude.
The uncontrolled or uneven, ragged opening of a parachute at high speeds is one of the major factors causing what are known as blown peripheries. These blown peripheries occur because a portion of the skirt of the canopy is blown inwardly through the space under the mouth and around another portion of the skirt.
Accordingly, another purpose of this invention is to control the opening of a parachute to decrease the risk of blown peripheries.
More specifically, it is a purpose of this invention to control the opening of the parachute in order to obtain repeatable air inflow conditions and hence repeatable, controlled opening times and opening loads.
In this application, certain terms will be used in the following fashion.
Folded refers to the condition where the parachute is entirely folded as it is when in the pack.
Deployed refers to the state when the parachute is first opened and the canopy material is strung out above the load or pilot but where there is little or no air in the parachute.
Squidded refers to the state immediately after the deployed state where there is some air in the canopy and its configuration is approximately cylindrical.
Reefing herein refers to the pulling in of the mouth of the canopy. It also refers to the restricting of the mouth of the canopy to less than its full projected area during terminal descent.